﻿<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
//来自：http://www.xker.com/page/e2008/0730/55115.html
    Color getRandColor(int fc, int bc) {//给定范围获得随机颜色
        Random random = new Random();
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }
%>
<%
//设置页面不缓存
            try {
                response.setHeader("Pragma", "No-cache");
                response.setHeader("Cache-Control", "no-cache");
                response.setDateHeader("Expires", 0);

// 在内存中创建图象
                int width = 60, height = 20;
                BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文
                Graphics g = image.getGraphics();

//生成随机类
                Random random = new Random();

// 设定背景色
                g.setColor(getRandColor(200, 250));
                g.fillRect(0, 0, width, height);

//设定字体
                g.setFont(new Font("Times New Roman", Font.PLAIN, 18));

//画边框
//g.setColor(new Color());
//g.drawRect(0,0,width-1,height-1);


// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
                g.setColor(getRandColor(160, 200));
                for (int i = 0; i < 25; i++) {
                    int x = random.nextInt(width);
                    int y = random.nextInt(height);
                    int xl = random.nextInt(12);
                    int yl = random.nextInt(12);
                    g.drawLine(x, y, x + xl, y + yl);
                }

// 取随机产生的认证码(4位数字)
                String sRand = "";
                for (int i = 0; i < 4; i++) {
                    String rand = String.valueOf(random.nextInt(10));
                    sRand += rand;
                    // 将认证码显示到图象中
                    g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
                    g.drawString(rand, 13 * i + 6, 16);
                }

// 将认证码存入SESSION
                session.setAttribute("rand", sRand);
// 图象生效
                g.dispose();
// 输出图象到页面
                ImageIO.write(image, "JPEG", response.getOutputStream());
                response.flushBuffer();
                out.clear();
                out = pageContext.pushBody();
            } catch (IllegalStateException e) {
                //System.out.println(e.getMessage());
                e.printStackTrace();
            }
%>